Apparatus for producing coherent bodies from asbestos dispersions

ABSTRACT

AN APPARATUS FOR PRODUCING ASBESTOS YARN FROM AN AQUEOUS DISPERSION OF ASBESTOS FIBERS COMPRISES SUPPLY MEANS FOR THE DISPERSION WITH A DISPENSING DEVICE FOR SHAPING THE DISPERSION INTO A TRAVELLING FILM STRIP ONTO THE SURFACE OF A MOVABLE CARRIER STRUCTURE. AS THE SURFACE TRAVELS PAST THE OUTLET OF THE DISPENSING DEVICE, IT ENTRAINS THE DISPERSION. APPLICATOR MEANS ARE PROVIDED FOR COVERING THE SURFACE OF THE CARRIER STRUCTURE WITH COAGULATING AGENT   SO THAT THE ENTRAINED DISPERSION COAGULATES TO A FILM STRIP MATERIAL WHILE IN CONTACT WITH THE CARRIER SURFACE. THE STRIP, AFTER SEPARATION FROM THE CARRIER SURFACE REACHES A POT-SPINNING DEVICE OR OTHER TWISTING MEANS WHICH IS LOCATED DOWNSTREAM OF THE CARRIER SURFACE AND TWISTS THE COAGULATED FILM STRIP TO YARN.

Sept. 28, 1971 w, DQNALDSQN ETAL 3,608,294

APPARATUS FOR PRODUCING COHERENT BODIES FROM ASBESTOS DISPERSIONSOriginal Filed April 14, 1969 6 Sheets-Sheet 1 Sept. 28, 1971 wDQNALDSON EI'AL 3,608,294

APPARATUS FOR PRODUCING COHERENT BODIES FROM ASBESTOS DISPERSIONS vOriginalFiled April 14, 1969 6 Sheets-Sheet 2 Sept. 28, w K. DONALDSONETAL APPARATUS FOR PKUDUUlNG COHERENT BODIES FROM ASBESTOS DISPERSIONSOriginal Filed April 14, 1969 6 Shoots-Shoot 5 p 23, 1971 A w. K.DONALDSON EFAL APPARATUS FOR PRODUCING UOHERENT noun-1s FROM ASBFSTOSDISPFRSIONS Original Filed April 14, 1969 6 Sheets-Shoot L Sept. 28,1971 w DQNALDSON ETAL 3,608,294

APPARATUS FOR PRODUCING COHERENT BODIES FROM ASBESTOS DISPERSIONSOriginal Filed April 14, 1969 6 Sheets-Sheet 5 Sept. 28, 1971 wDONALDSON EI'AL 3,608,294

APPARATUS FOR PRODUCING COHERENT BODIES FROM ASBESTOS DISPERSIONSOriginal Filed April 14, 1969 6 Sheets-Sheet 6 United States Patent3,608,294 APPARATUS FOR PRODUCING COHERENT BODIES FROM ASBESTOSDISPERSIONS William K. Donaldson, 23 Cringle Drive, Cheadle, Cheshire,England; and Werner Wilke, Schillerstrasse 34; and Hans Fetzer,Emil-Kostweg 5, both of Schwabisch Hall, Germany Application Apr. 14,1969, Ser. No. 839,748, which is a continuation-in-part of applicationSer. No. 510,246, Nov. 29, 1965. Divided and this application June 9,1969, Ser. No. 831,783 Claims priority, application Great Britain, Dec.4, 1964, 49,445/ 64; May 7, 1965, 19,469/65; Austria, May 3, 1966, A4,176/66; Dec. 23, 1966, A 11,853/66 Int. Cl. D02g 3/06, 3/20 US. Cl.57-35 5 Claims ABSTRACT OF THE DISCLOSURE An apparatus for producingasbestos yarn from an aqueous dispersion of asbestos fibers comprisessupply means for the dispersion with a dispensing device for shaping thedispersion into a travelling film strip onto the surface of a movablecarrier structure. As the surface travels past the outlet of thedispensing device, it entrains the dispersion. Applicator means areprovided for covering the surface of the carrier structure withcoagulating agent so that the entrained dispersion coagulates to a filmstrip material while in contact with the carrier surface. The strip,after separation from the carrier surface reaches a pot-spinning deviceor other twisting means which is located downstream of the carriersurface and twists the coagulated film strip to yarn.

This is a division of our copending application Ser. No. 839,748, filedApr. 14, 1969, for Production of Coherent Bodies From Fluids, which is acontinuation-in-part of the application Ser. No. 510,246, filed -Nov.29, 1965, now abandoned, and claims priority rights based upon twoBritish application filed Dec. 4, 1964 and May 7, 1965, and two Austrianapplications filed May 3, 1966 and Dec. 23, 1966.

This invention relates to apparatus for the production of coherentbodies composed predominantly of asbestos from an aqueous dispersion ofasbestos fibers and a reagent by causing the reagent to react with acoagulating liquid to produce a precipitate that binds the fibers. Thereagent in the dispersion may, for instance, be a soluble soap and thecoagulating liquid which the dispersion enters may be a solution inwhich there are cations of a polyvalent metal or hydrogen or both sothat the soluble soap is converted into a water-insoluble soap or awaterinsoluble fatty acid, which is the binding agent. In apparatusaccording to the invention any reagent and any coagulating liquid whichwill react to form a binder may be used, but most conveniently thereagent is a sodium soap and the coagulating liquid is a solution ofaluminium sulphate or zinc sulphate.

Asbestos dispersions of the kind in question, which are usually ofchrysotile asbestos, may be made with either one or more than onedispersing agent. A water-soluble soap used as the reagent for thesubsequent coagulation acts also as a dispersing agent. The dispersionstend to be unstable, and begin to coagulate not only on contact with acoagulating liquid but also if they are diluted. A typical dispersion issomewhat viscous, say of the viscosity of cream.

The invention is based on the observation that when such a dispersionand coagulating liquid are so brought into contact with one another thatthere is an interface between them a film is formed which can becontinuously drawn away from the interface.

3,608,294 Patented Sept. 28, 1971 According to this invention,dispersion in a pool is subjected to traction by an endless carrier thatis wet with the coagulating liquid so that a layer of dispersion isremoved, the surface of the layer in contact with the carrier being atleast partly coagulated and the opposite surface of the layer beingexposed to air and out of contact with any transverse solid surface suchas a doctor blade or roller while it remains uncoagulated, someuncoagulated dispersion at this exposed surface of the layer is causedto pass back against the movement of the carrier so as to lea ve on thecarrier a partially coagulated film of dispersion with an exposed face,further coagulating liquid is applied to the exposed face of the film,and the film is stripped from the carrier during or after theapplication of the further coagulating liquid.

The carrier, it will be seen, must carry a layer of dispersion with it,and for this to be done there must be an interface between the carrierand the pool. The object is to produce a thin uniform film which cansubsequently be stripped from the carrier, and it is therefore necessaryto prevent excess dispersion from being carried forwards. This excessdispersion may run backwards under the influence of gravity if thesurface of the carrier moves upwards away from the pool. The excessdispersion can also be moved backwards by an air blast, and such a blastmay be used to assist the action of gravity.

There are various ways of ensuring that an interface continuously existsbetween the carrier and the pool. Thus, the surface of the carrier maymake contact with the upper surface of the pool of the dispersion, or bedipped into the pool.

Particularly advantageously the surface of the carrier may form anupwardly moving end wall of a trough or other vessel that contains thepool. Again the pool maybe formed on the surface of the carrier byapplying dispersion to that surface. If this is done at a point wherethe surface is moving upwards, the dispersion tends to run down thecarrier but a layer is carried upwards. If an air blast is used to moveexcess dispersion in the layer against the movement of the carrier, thesurface of the carrier may be horizontal or even slightly downwardlyinclined at the point where the pool is formed.

In such apparatus according to the invention the film is formed at aninterface between the carrier and the pool, and the carrier does notcooperate with any other surface to form a channel which determines theshape of a body of the dispersion. Hence there is no orifice, or narrowgap between the carrier and another surface, through which thedispersion passes and which could be blocked by small bundles ofundispersed fiber or by foreign bodies such as are regularly found inthe raw asbestos from which dispersions are formed.

It follows also that the cross-sectional dimensions of the film areformed inter alia by the flow characteristics of the dispersion and thegeometry at the interface.

It is found best to restrict the amount of coagulating liquid carried tothe interface by the carrier, primarily because any excess ofcoagulating liquid may run oflf the carrier into or onto the pool andform clots in the pool.

The endless carrier may be either a belt or a drum, and in either caseit may have a porous or an impermeable surface; moreover, it may beporous throughout and not only on the surface. A carrier with acompressible porous surface carries coagulating liquid to the dispersionreadily, and in fact should be compressed by a roller to expel excesscoagulating liquid after the film has been stripped. There is nodifficulty in stripping the film from a porous carrier that is wet withcoagulating liquid, because soluble soap or fatty acid will not enterthe pores if they either contain or have their walls wetted with acoagulating liquid. Instead a layer of insoluble soap or fatty acid (andfibers) is formed immediately on the carrier, but

no part of this layer penetrates beyond the surface irregularities ofthe carrier. It is easy to strip off such a layer.

A carrier with an impermeable surface is effective provided that it isuniformly wetted with coagulating liquid.

The carrier may also be a gauze, such as the wire gauze used in aFourdrinier paper-making machine.

After the removal of excess coagulating liquid, the layer is onlypartially coagulated. Although sulphate or other coagulating liquid willdiffuse into the film from the carrier until this is stripped from thecarrier, the applications of further coagulating liquid to the exposedface is required in order rapidly to complete the coagulation necessaryto render the film adequately strong for stripping and subsequenthandling. Although this further coagulating liquid may be sprayed ontothe film, it is preferred to provide it as a bath into which the film iscarried. In accordance with the thickness of unreacted dispersioncarried away by the film, which in turn depends to some extent upon theviscosity of the dispersion, the length of the bath of coagulatingliquid through which the film is carried to complete the reaction of thedispersion on it may be from 1 to 20 feet.

The film is stripped from the carrier at some convenient point in itsrun, which may be outside the bath of coagulating liquid or in thatbath. Stripping in the bath presents the advantage that coagulatingliquid can act on the inner surface of the film as this film isstripped, and thus assist in ensuring that the reagent in the film ofthe dispersion reacts completely. The stripped film may be led to adraw-off wheel.

Once a skin has been formed on the exposed surface of the film thecross-sectional dimensions are essentially determined. Even so it isdesirable that after being stripped the film should not come intocontact with any transverse surface until coagulation is complete. Ifthere is uncoagulated dispersion inside a coagulated outer skin of thefilm at a time when the film is subjected to any pressure such as may beexerted by passage in contact with a scraper blade or over a roller, theuncoagulated dispersion tends to move backwards inside the film and toform a bubble, which bursts and breaks the film.

The film may be stripped from the carrier by hand at the start of theprocess, but may break in the course of continuous operation. Thefollowing film may then adhere to the carrier. Although it may be inturn stripped by hand, automatic stripping is desirable. This may beeffected by a jet of fluid, which is preferably coagulating liquid,directed at the carrier. This jet may flow throughout the Wholeoperation. When the leading edge of the partially coagulated film hasbeen lifted from the moving carrier, stripping of the film continues asthe carries moves past the jet. The film so removed swims about in thecoagulant bath and is readily picked out by the operative and linked toa draw-off wheel. If there is continuous fiow of the coagulating liquidthrough the bath towards a weir and a draw-off wheel is placed at theweir, the free end of the film may be carried to and over the weir to becaught by the draw-off wheel automatically.

After the excess dispersion has been removed, the film composedpartially of coagulated dispersion and partially of unreacted dispersionmay be up to about half a millimeter thick. The stripped film is wet,and it may, if desired, be dried before or after reaching the draw-olfwheel. An important final product of the invention is yarn, which may beformed by spinning a film, two or more narrow films, or a strip orstrips slit from a wide film. The film or strip may be twisted or spunwet, or may be dried, either by mere exposure to air or by heat. Thefinal thickness of the film, if dried fiat, may be say, one-hundredth ortwo-hundredths of a millimeter.

The carrier may vary very considerably in Width, from for example 1millimeter in order to produce a line yarn to 1000 or more millimetersin order to produce a paper like product. A number of parallel narrowfilms may be formed on a single carrier.

As an example, the dispersion may be made with the use of two dispersingagents, namely a water-soluble soap and another anionic surface-activedispersing agent, and may have the following composition by weight:

Parts Tap water of hardness of about 30 p.p.m. expressed as calciumcarbonate (at C.) 1100 Chrysotile asbestos (Grade 2) 20 Sodium dodecylbenzene sulphonate 1.2

Soap (sodium salts of mixed long-chain fatty acids, average watercontent 20%) Aluminium sulphate 0.7

Thecoagulating liquid may be a 5% solution of zinc sulphate in water. Wefind that a continuous film can be formed from such a dispersion andcoagulating liquid at a rate of 20 meters per minute.

The dispersion may contain other particles or fibers, which may becolloidally or non-colloidally dispersed. Examples are particles ofpolymers or graphite and glass fibers. These particles or fibers becomepart of the film, either by reaction or by mechanical entrainment.Emulsions and latices, for example of rubber, may also be present andbecome part of the film.

The invention may be carried out in various forms of apparatus, some ofwhich are shown diagrammatically in the accompanying drawings, in which:

FIG. 1 shows one form of apparatus;

FIG. 2 shows one form of vessel that may be used to hold the dispersion;

FIG. 3 shows part of another apparatus in elevation;

FIG. 4 is a section on the line IV-IV in FIG. 3;

FIGS. 5, 6 and 7 show three further forms of apparatus;

FIG. 8 illustrates the use of an air blast;

FIG. 9 shows another form of apparatus; and

FIG. 10 is an elevation and FIG. 11 is a plan of yet another form ofapparatus.

In the apparatus shown in FIG. 1, a pool of dispersion is maintained ina vessel 1 having an overflow weir 2 at one end, fresh dispersion beingpumped in at the other end through a pipe 3 by a pump 4 from a reservoir5 so that there is a continuous flow through the vessel. A roller 6around which a porous endless belt 7, wet with coagulating liquid, runsis disposed so that as the belt passes beneath the roller its surfacemakes contact with the surface of the pool. Over the area of contactbetween the belt and the pool the belt exerts traction on thedispersion, and it carries a layer of dispersion out of the pool. Someof this layer runs backwards into the pool to leave a film on the uppersurface of the belt as this runs upwards from the roller 6 to pass rounda roller 8. The belt then travels approximately horizontally to runround another roller 9 from which it travels downwards to enter a bathof coagulating liquid in a tank 10 in the bottom of which there is afurther roller 11 round which the belt runs to travel out of the tank.It is found that in the downward run of the belt unreacted dispersion onthe belt may move downwards and create irregularities in the film. Itmay therefore be advantageous to spray coagulating liquid onto the filmthrough a nozzle 12 at a point where the belt is running horizontally,in order to increase the amount of reaction that takes place before thefilm becomes vertical.

The film is stripped from the belt as the latter begins its upward runin the tank 10 and travels for some distance through the bathunsupported by the belt. On leaving the bath it passes over a draw-offroller 14 from which it travels over a further roller 15 to apot-spinning device 18.

The belt travels onwards and out of the tank, carrying coagulatingliquid with it. On leaving the tank 10 the belt 7 passes through a nipbetween the roller 8 and a roller 16 to remove some but of course notall of the liquid it carries, and then back to the pool of dispersion.The liquid removed is caught by a trough 13. The belt may be engaged bya brush to clear away any fibers from it that have not been removed fromit on the stripping of the film.

For the reason given above, the depth of the bath of coagulating liquidin the tank and the speed of the belt should be so correlated that thefilm does not come into contact with the draw-off roller or any otherhard surface until it is coagulated throughout its thickness.

For successful continuous operation it is necessary that a dispersion ofconstant concentration and a coagulating liquid of constantconcentration shall be brought into contact at the surface of the belt,that is to say, at the interface between the belt and the pool. Some ofthe coagulating liquid may diffuse into the pool of dispersion.Moreover, there may be some dilution of the dispersion by reactionproducts as a result of the reaction. The dispersion will not remainstable if its concentration varies to any great extent, and if theconcentration does vary it is necessary continuously to replace thedispersion at the area of contact by fresh dispersion. This is done inthe apparatus shown in FIG. 1 by causing the dispersion continuously toflow through the pool in a circulatory system, and restoring itsconcentration in the course of the circulation. In the course of thisconcentration any undesired reaction products should be neutralized.Conveniently a main supply of dispersion entering the reservoir througha pipe 17 may be rather more concentrated than is desired in the pool sothat when it is mixed with the somewhat diluted dispersion flowing overthe weir 2 a dispersion of the proper concentration is formed.

When the process is carried on in an apparatus of the kind shown in FIG.1 the fibers are predominantly oriented in the direction of movement ofthe belt. Although this gives high strength in one direction it alsogives low extensibility. In order to produce a film with more randomorientation the dispersion should be decelerating on arriving at thearea of contact. Such deceleration may be produced by appropriatelyshaping the vessel that holds the pool. For example, as shown in FIG. 2,the base of a vessel that contains the pool of dispersion may slopedownwards as shown at 19 beneath the roller 6 so that over the area ofcontact the dispersion is decelerating. It is then desirable that theactual velocity at the area of contact should be very much the same asthat of the belt 7. Again the dispersion may be passed through thevessel parallel to the axis of the roller 6 so that the fibers will bepredominantly oriented transversely to the belt 7.

When the carrier is a porous belt, as in the apparatus shown in FIGS. 1and 2, it absorbs excess solution, that is to say undesired reactionproducts, from the film. Thus the risk of dilution of the dispersion oraccumulation of undesired products at the area of contact of the beltwith the pool is low, and it may be unnecessary continuously to replacethe dispersion there by fresh dispersion. The belt is preferablycomposite, comprising a non-porous backing and a layer of compressibleabsorbent sponge or other porous material.

In the apparatus shown in FIGS. 3 and 4, a pool of dispersion ismaintained in a trough 20 having an end which is formed with verticalslots 21. The carrier is a belt 22 that runs round a drum 124. Theslotted end of the trough 20 is placed against a curved, upwardlymoving, part of the carrier 22 so that it forms a tangent, approximatelyat the bottom of the slots 21. The dispersion flows through each slotand across the intervening gap towards the carrier to be carried upwardsas layers 23, which tend to spread out sideways as shown. Excessdispersion runs backwards, to leave films each of width greater than thewidth of the slot by an amount depending on the height of the freesurface of the dispersion above the level where the slot structure formsa tangent to the carrier. The carrier 22 should be close enough to theend of the trough 20, and run upwards at a speed high enough, to ensurethat any dispersion tending to run downwards from the base of the troughis picked up and carried away by the carrier before it can do so. Thecarrier on leaving the drum runs downwards into a bath of thecoagulating liquid.

Dispersion is delivered to the trough at a constant rate, and should beremoved as film at exactly the same rate.

The slots shown in FIGS. 3 and 4 are particularly suitable when theobject is to produce a number of narrow films to be twisted together toform yarn. If a wide film is required, the end of such a trough as thatshown at 20 may be wholly open. Its side Walls may be curved to matchthe path of the carrier, and preferably are upwardly divergent.

It will also be appreciated that the carrier cooperating with a troughthat has either an open or a slotted end may be a drum.

In one apparatus with a slotted trough, there were nine slots, each 4mm. wide, to produce nine films. The slots started at the bottom of thetrough 20 and extended upwards for 52 mm. The slotted wall of the troughwas fiat and formed an angle of 97 with the base. The base was locatedin a horizontal plane close to the horizontal axis of a sponge-covereddrum mm. in diameter. Dispersion was fed continuously into the trough,and in operation it stabilized at a depth of 25 mm. There were ninestrips of film each about 6 mm. wide before being stripped from thecarrier.

FIG. 5 shows an apparatus of somewhat difierent and simpler layout. Thebath of coagulating liquid is in a shallow horizontal tank 24 instead ofa vertical tank as shown in FIG. 1. A gauze belt carrier 25 is used andruns round only two rollers 26 and 27 and picks up dispersion from atrough 28 that resembles the trough 20. There is a reservoir 29 ofcoagulating liquid from which a pump 30 draws liquid continuously anddelivers it to a nozzle 31 from which this liquid passes as a jet ontothe upper side of the lower run of the belt 25, thus performing twofunctions. The first is to clear the belt of any fibers it may becarrying, and the second is to strip the film, shown at 32, from thebelt both initially and if it should break. The belt passes between tworollers 49 for the removal of excess liquid. The stripped film travelsthrough the coagulatting liquid in the tank 24 to a draw-off roller 33over which a perforated belt 34 passes. From the belt the film 32travels downwards to a pot-spinning device 35. The spinning impartstension to the film, and it is undesirable that this tension should beapplied to the film at any point when this is not fully coagulated.Accordingly a small nip roller 33 is provided to engage the film on theroller 33. Liquid runs down with the film to the pot-spinning device 35,as-

sisting to strip the film from the roller 33, and flows from the device35 through a pipe 36 into a tank 37. A pump 38 draws from this tank todeliver liquid to and through a nozzle 39 to strip the film ifnecessary. Excess liquid runs from the tank 37 to waste through anoverflow 40.

Coagulating liquid continuously flows out of the tank 24 and through thebelt 34 into a hopper 41, from which it is returned through a pipe 42 tothe reservoir 29. Fresh coagulating liquid is supplied to the reservoir28 through a pipe 43.

If instead of a gauze belt a compressible porous belt such as that shownin FIG. 1 is used, the jets must of course be otherwise arranged. Thisdifferent arrangement is shown in FIG. 6, in which there is a porousbelt 44 stripped by coagulating liquid delivered through a nozzle 45. Inthis figure the film 32 passes over a perforated draw-ofi wheel 46 andis stripped by a jet from an internal nozzle 47. The application ofspinning tension to the film before it reaches the wheel 46 is preventedby a nip roller 46'. The wheel is washed by coagulating liquid leavingthe tank 24 and flownig into a hopper 48.

FIG. 7 shows an apparatus in which the carrier is a drum 50 that picksup dispersion from a trough 51 and forms one wall of a container 52 forcoagulating liquid. The bottom of this container is formed by a chute53-, and the drum 50 nearly comes into contact with this chute. A

bafile 54 is provided in the container 52 to separate that part of thecontainer to which coagulating liquid is supplied from the drum, so thatthere is a quiet pool of liquid close to the drum. The dispersion at theexposed face of the film reacts with liquid in this pool, and moreliquid runs continuously down the chute 53 in contact with the film.

A jet of stripping liquid is supplied through a nozzle 55, being drawnfrom a reservoir 56 by a pump 57. This jet clears the drum if there isany breakage and yet the film is fed forwards, passing down the chute53.

By the time the stripped film reaches the end of the chute 53 thecoagulation is complete. The film passes over a draw-off wheel 58 andexcess coagulating liquid flows over the end of the chute into thereservoir 56. From this reservoir the liquid is pumped by a pump 59 tothe container 52, as well as by the pump 57 to the nozzle 55.

It will be understood that there may be several nozzles 55 deliveringstripping jets if desired.

FIG. 8 shows part of an apparatus in which the pool is maintained in atrough similar to the troughs shown in FIGS. 3 to 7. In this apparatus acurrent of air is used to assist the action of gravity in causing excessdispersion carried away from the pool to return to the pool. A carrier72 Wet with coagulating liquid moves upward past a pool of dispersion 73in a trough 74. In this figure the very thin, partially coagulate'd,layer at the surface of the carrier is shown at 78 and the layer drawnupwards at 77. A jet of air 75 issuing from a nozzle 76 is directedagainst the layer 77 of dispersion on the carrier so that excesscoagulating liquid is returned to the pool 73 at the surface of thelayer 77 and only a limited amount passes forward with the carrier 72 toform a thin film 79, which is subsequently coagulated completely beforeor after being stripped from the carrier.

FIG. 9 shows an apparatus in which the dispersion is formed into a poolon the surface of a carrier. This carrier is an impermeable belt 60which runs round three rollers 61, 62 and 63, the last being immersed ina bath of coagulating liquid in a tank 64. The carrier 60 runs upwardsfrom the roller 61 to the roller 62 and in the course of the upward runreceives dispersion fed at a constant rate through a pipe 65 thatterminates in. a spout 66. The dispersion forms a pool On the carrier60, which carries a layer away from the underside of the pool. Some ofthis layer runs backwards to the pool, and some spreads itself out toform a film 67. This film is carried into the coagulating liquid in thetank 64. The coagulated film, shown at 68, is stripped by a jet ofcoagulating liquid delivered through nozzle 69 and drawn otf over aroller 70. Excess coagulant is removed from the carrier 60 by a scraper71.

The apparatus shown in FIGS. and 11 is similar to that in FIG. 9 exceptthat the action of gravity in causing some of the layer to movebackwards and spreading the layer across the carrier is replaced by theaction of a current of air. A carrier 80 wetted with coagulating liquidmoving in an approximately horizontal plane. It receive's a stream 81 ofdispersion issuing from a spout 82. Thls stream is carired along as alayer, and it is struck by a jet of air 83 issuing from a nozzle 84.This jet blows the upper part of the layer backwards so that the layerincreases in depth and spreads sideways, forming a pool 85 of greaterdepth than the layer. Uncoagulated dispersion is carried forwards, withthe layer of coagulated dispersion that is in contact with the surfaceof the carrier, as a film 86. The pool 85 is stable in that the mass offibers removed in the film 86 in unit time equal the mass of fiberswhich is fed onto the carirer 80 by the stream 8 1. The carrier 80subsequently carries the film 86 to a bath of coagulating liquid.

In all the apparatus excess coagulating liquid may be removed from thecarirer in various ways, for example by being scraped by a blade orblades. If the carrier is of gauze, it may pass through the nip betweentwo rollers one of which has a porous compressible surface. Again excessliquid may be removed from a gauze carrier by suction. Again, if a gauzeor impermeable carrier travels slowly enough, natural drainage may beadequate and no special steps need be taken to remove coagulating liquidfrom it before it again comes into contact with the pool of dispersion.

As described above, the invention atfords the production of asbestosyarn by spinning or twisting the film strip or the several strips ofcoagulated asbestos dispersion after they have been stripped from themoving carrier surface. In the abovedescribed embodiments illustrated inFIGS. 1 and 5, such twisting of the strips is effected by continuouslypassing the strips to a pot-spinning device (18 in FIG. 1, 35 in FIG. 5)at the end of the strip travel. Each rotation of the spinning potimparts one turn of twist to the material being spun. For example, a potspeed of 3000 rpm, at the abovementioned delivery rate of 28 m./min.,would result in twisting yarn about times per running meter. As to thetwisting effected by pot spinning, reference may be had to (1) EberMidgley, Technical Terms in the Textile Trade, vol. II, published 1932by Emmott & Co. Limited, London (page 207); (2) George E. Linton, TheModern Textile Dictionary, published 1954 by Duell, Sloan and Pearce,New York (pages 510 and 628); (3) McGraw-Hill Encyclopedia of Scienceand Technology, 1960 (page 618); or also to the copending application ofWilke et al., Ser. No. 681,050, filed Oct. 23, 1967, now Patent No.3,475,894.

We are aware that, in retrospect, the production of a film strip upon amoving carrier according to the invention may be found to be comparableto similar method steps known in the manufacture of products fromorganic and non-fibrous substances, such as rubber and plastics,dissolved or emulsified in organic solvents. Heretofore, however, theindustries and persons dealing with asbestos production techniques havebeen unaware of the useful potentiality inherent in the tendency ofaqueous asbestosfiber dispersions to form, on contact with acoagulantwetted surface, a coherent film capable of being stripped as awhole from the carrier. Also remarkable in this respect is the highproduction rate attainable by the invention, such as the abovementionedrate of 20 m./min. achieved with a dispersion although it contained 55'times more water than asbestos fibers, for example. While a dispersionor emulsion of an organic liquid in a solvent will tend to form a filmof fully homogeneous constitution when a structure wetted with coagulantis dipped into such a liquid, no such homogeneity can be obtained if acarrier surface wetted with coagulant is passed through a dispersion ofasbestos fibers, i.e. an inorganic nondissolved material. Hence, itshould be expected that at best a layer of unoriented fibers Will bedeposited and that such a layer will exhibit only slight coherence andnot be directly suitable for further fabrication. It is a surprisingphenomenon, applied to advantage by the present invention, that acontact-entrainment deposition of films can also be successfully andadvantageously carried out with aqueous asbestos dispersions and willresult in high quality strands of uniformly oriented fibers imparting tothe film the mechanical strength and coherence required for strippingthe film and spinning it to yarn.

We claim:

1. Apparatus for producing asbestos yarn from an aqueous dispersion ofasbestos fibers, comprising supply means for said dispersion, saidsupply means having a dispening device for shaping the dispersion into atravelling film strip, said device having a dispersion outlet, movablecarrier structure having a conveying surface movable past said outletand engageable by the dispersion issuing from said outlet for subjectingsaid issued dispersion to traction in the travel direction of thecarrier structure, applicator means for applying coagulating agent tosaid surface so that the dispersion at least partially coagulates to afilm material while in contact with said carrier structure, and meanslocated downstream of said carrier structure and of said applicatormeans and engageable with the cogulated strip material for convertingthe coagulated strip material to yarn in continuous operation.

2. Apparatus for producing asbestos yarn from an aqueous dispersion ofasbestos fibers, comprising supply means for said dispersion, saidsupply means having a dispensing device for shaping the dispersion intoa travelling film, said device having a dispersion outlet, movablecarrier structure having an endless conveying surface rotatably movablepast said outlet and engageable by the dispersion issuing from saidoutlet for subjecting said issued dispersion to traction in the traveldirection of the carrier structure, applicator means for applyingcoagulating agent to said surface so that the dispersion at leastpartially coagulates to a film material while in contact with saidcarrier structure, and twisting means located downstream of said carrierstructure and of said applicator means and engageable with thecoagulated material for twisting the coagulated material duringcontinuance of its travel so as to produce yarn from the dispersion incontinuous operation.

3. In apparatus according to claim 1, comprising a container arrangedfor holding coagulating agent so that said carrier structure can dipinto the agent, and a transport member for removing the coagulatedmaterial from the 10 carrier structure and passing it in solidifiedcondition to said twisting means, said transport member being mounteddownstream from where the carrier structure dips into the coagulatingagent.

4. Apparatus according to claim 2, comprising means for forming saidfilm material on said conveying surface into a multitude of longitudinaland parallel strips to be twisted together by said twisting means.

5. In apparatus according to claim 2, said yarn-forming means being apot-spinning device.

References Cited UNITED STATES PATENTS 1,542,915 6/1925 Sherman 57-311,590,999 6/1926 Czapek et al. 264215 2,871,652 2/1959 Schwartz 57167X3,398,220 8/1968 Port et a1 57-16-7X 2,578,941 12/1951 Novak et a1.57156 2,972,221 2/1961 Wilke et al. 57164 FOREIGN PATENTS 675,28312/1963 Canada 264215 DONALD E. WATKINS, Primary Examiner US. Cl. X.R.264-212

